On 1996.4.26 Gabriel Roy wrote: >Mr. Varju gave a very good summary of the requirements to Mr. Lee, but I need >to clarify that there has been an update to the 12 Megohm max. static discharge
>resistor requirement. That resistor has been replaced by a high voltage surge >test. >The reference is UL Bulletin dated November 9, 1995, under subject 1950. >Section 5 of the bulletin reported on the results of the Binational AdHoc group >on "ITE with provisions for connections to outdoor antenna and cable systems" >(pages 7 through 10 of the bulletin). The conclusion, found on page 10, is that >UL now requires a voltage surge test instead of the static discharge resistor. >The surge is either per IEC 65 (50 discharges from a 1 nf capacitor charged to >10 KV), or per UL 1492 (4 discharges from a 0.1 uf capacitor charged to 10 KV). >The manufacturer has the option of either test. The manufacturer does NOT have >the option of using the resistor in lieu of the test, however. >The effective date of that requirement was set as "upon publication" (page 3 of >the bulletin). Since there were no comments from the industry in the 30 days >allocated for response to the bulletin, this translates into the requirements >being effective NOW. And by NOW, I mean that the surge test was enforced on my >equipment in February of this year. >Presently Listed constructions using the static discharge resistor will >continue to be Listed and will not have to be subjected to the voltage surge >test. to maintain the Listing. >An interesting sideline is that this applies to both the Second and the Third >edition of UL 1950, meaning that it also applies to the binational Standard >(i.e. the Ad Hoc committee was Binational, the Third Edition is Binational, and >CSA should also be enforcing this). Well ... Actually things are not quite that simple. Since CSA950/UL1950 is a binational standard, the requirements can only change after approval by both Canada and the US and are effective only after publication. Neither UL nor CSA have published any revised requirements regarding the subject matter. It is my understanding that no firm decisions have yet been reached by either UL or CSA regarding the acceptance of the Ad Hoc committee's recommendation, or the actual final requirements that may be published. Recent discussions with UL engineers (this week!) confirm that they are still requiring the discharge resistor. Though some agency engineers may opt to apply these "draft" requirements, in the meantime, the discharge resistor is still acceptable, since it is a published requirement that has not yet been rescinded. If anybody knows more about this subject, I'd love to hear from you! Egon Varju PS: The above are personal opinions that don't necessarily reflect the position of CSA.
